Ice detection/protection and flow control system based on printing of dielectric barrier discharge sliding plasma actuators

ABSTRACT

The system comprises the following components: exposed AC electrode (1), dielectric layer (2), embedded electrode (3), sliding/nanosecond electrode (4), ground plane (5), AC power supply (6), DC power supply (7), nanosecond range pulse generator (8), monitoring capacitor (9), high voltage probe (10), control module (11), temperature sensor (12), control signal input module (13) and monitoring system (14). The system senses ice formation and generates extensive surface heating to prevent ice accumulation.

TECHNICAL DOMAIN

The present invention relates to a smart ice detection, and protectionand flow control system based on printing of dielectric barrierdischarge sliding plasma actuators.

SUMMARY

The present invention discloses a system capable of controlling the flowand simultaneously performing ice detection, preventing ice formationand deicing on surfaces by making use of a dielectric barrier dischargesliding plasma actuator.

Generally, most in-flight aircraft deicing and anti-icing methods onlyprotect the surfaces and the most critical components of the aircraft.The present invention is useful for detecting and preventing theformation of ice on aircraft surfaces and has the following mainadvantages: reduced weight, low maintenance cost, no environmentalimpact, an electronic operation and the combination of a deicing andanti-icing system with a flow control system and ice detection sensors.

The present invention can be applied to any type of surfaces withoutgreat complexity. It can operate continuously in anti-icing mode orintermittently in deicing mode. When a sufficient high voltage level isapplied to this system, the surface temperature rises to a temperatureabove the melting temperature of water and the surface heating due tothe operation of the dielectric barrier discharge plasma actuatorprevents the accumulation of ice on the front edge of the wing. Inaddition, if at high pulse voltage of the nanosecond order is applied tothe actuator, it will induce shock waves to the surface that expel theice and further remove ice that may accumulate after the portion of thesurface area, which is effectively heated and protected. The energyconsumed by the present invention is lower than that of most traditionalice accumulation protection systems, and has a flow control capacity,which allows the reduction of resistance and noise.

In parallel, this invention further relates to a smart anti-icing anddeicing system based on plasma actuators, which can be used as anice-formation detection sensor in order to detect the start of itsformation and to warn if a critical ice level is achieved.

Using circuit-printing technology to produce this system, temperatureand pressure sensors can be easily printed along with dielectric barrierdischarge plasma actuators. In this way, the application of this systemensures that the various sensors outside the aircraft are free of iceand snow.

The present invention describes an ice detection/protection and flowcontrol system comprising at least one dielectric barrier discharge(DBD) plasma actuator, DC power supply, AC power supply, a nanosecondrange pulse generator, and a control module, applicable on any surface,wherein the plasma actuator acts as an ice-forming sensor, controls theflow and performs the surface deicing, and comprises a dielectric layer,a monitoring capacitor connected in series and three electrodesconnected to a high voltage generator.

In one embodiment, switching between the ice detection, anti-icing anddeicing operating modes is carried out by controlling the power suppliescontrolled by the control module.

In another embodiment, the surface temperature reaches temperaturesabove 120° C. when the plasma actuator is energized by pulsed voltage of50 ns.

In yet another embodiment, two electrodes are exposed and positioned onthe surface of the dielectric layer.

In one embodiment, the dielectric layer covers one of the electrodes.

In one embodiment, the exposed AC electrode is energized by AC voltage,the exposed sliding/nanosecond electrode is energized by DC voltage witha tendency for nanosecond pulses, and the embedded electrode, which isseparated from the electrodes exposed by the dielectric material, is notexposed to air and is connected to the ground plane.

In another embodiment, the exposed DC voltage-energized electrode isalso energized with nanosecond voltage pulses in the range of 10 ns to100 ns.

In one embodiment, the AC high voltage signal applied to the exposed ACelectrode has a voltage amplitude between 5 and 80 kVpp and frequenciesbetween 1 and 60 kHz.

In another embodiment, the monitoring capacitor is connected to theground plane and monitors variations of the electric field of the plasmaactuator.

In yet another embodiment, the system comprises at least one temperaturesensor.

In one embodiment, the system comprises a control signal input module.

In another embodiment, the control module activates the power supply,which adjusts the input signals from the exposed electrodes.

In yet another embodiment, the operating voltage is measured from a highvoltage probe.

In one embodiment, the system comprises a monitoring system.

In another embodiment, the plasma actuator is manufactured by circuitprinting technology with embedded temperature sensors.

In yet another embodiment the system is used on aircraft surfaces.

PRIOR ART

The invention described herein is based on a system that enhancesdeicing and anti-icing efficiency through a dielectric barrier discharge(DBD) sliding actuator and an electrode energized by nanosecond rangepulses which enable the detection of ice through the DBD actuator thatacts as an ice-forming sensor.

WO 2014/122568 [1] discloses a system for preventing the formation ofice on the surface of aircrafts comprising a DBD plasma actuator. Thesystem has been designed to use alternating voltage modulated atdifferent frequencies and amplitudes and also in pulsed mode. Thissystem uses the surface temperature as a signal to the control modulethat activates the deicing system and can be manufactured by circuitprinting. Although this system uses DBD plasma actuators to performdeicing, it does not use the DBD plasma actuator as an ice detectorsensor. In addition, the area covered by the actuator is limited, andsince it contains only one electrode exposed per actuator, it does notcontain any type of mechanism to control the accumulation of ice in thearea that is not effectively heated by the actuator.

EP 2365219 A2 [2] and U.S. Pat. No. 8,038,397 B2 [3] describe an airturbine blade deicing system which includes an electrically poweredplasma actuator applied to a desired area of the air turbine blade. Theplasma actuator is connected to the power supply, which includes awaveform controller configured to control the input voltage level, pulsewidth, frequency, duty cycle, and waveform. The system described hereinmay be manufactured in the form of tape, which can be applied todifferent surfaces. Although DBD plasma actuators are used in the abovesystem to perform deicing, this type of system does not include an icedetector sensor. On the other hand, the area encompassed per actuator islimited and, since it only contains an electrode exposed per actuator,it does not contain any type of mechanism to control the accumulation ofice in the area that is not effectively heated by the actuator.

CA 2908979 A1 [4] relates to a separating tip of an axial turbomachinewith a deicing system. The disclosed device has two annular layers ofdielectric material partially forming the separation surface, anelectrode forming the upstream edge, an electrode forming the outer wallof the separating tip, an electrode forming the outer shell supportingthe blades and an electrode that delimits the primary flow. The devicegenerates plasmas that oppose the presence of ice in the partitions ofthe separating tip by making use of a power supply, which provides asinusoidal or square alternating voltage signal with periods of a fewnanoseconds. Although the above system makes use of DBD plasma actuatorsfor performing deicing, this system does not include an ice detectorsensor, the area covered per actuator is limited and, since it only hasone exposed electrode per actuator, it does not contain any type ofmechanism to control the accumulation of ice in the area that is noteffectively heated by the actuator.

WO 2015024601 A1 [5] discloses a system for controlling the boundarylayer of a fluid flow on the surface of a body. The system comprises ananosecond range pulse plasma actuator with dielectric/resistive barrierdischarge and a surface pressure measurement tip, which allows themeasurement of flow characteristics and subsequent emission of signalsto a controller that activates the system. Through this invention, lowefficiency and low yield problems of NS-DBD plasma actuators were solvedand a device, system and method were provided that allow performingdifferent tasks within the scope of active flow control. For thispurpose, the dielectric barrier was considered to be resistive ordielectric, and the use of a resistive barrier, instead of a dielectricbarrier, allows manipulation of the thermal effect, which in turnbroadens the field of applications. Although the above system makes useof DBD plasma actuators for performing deicing, this system does notinclude an ice detector sensor, the area covered per actuator is limitedand, since it only has one exposed electrode per actuator, it does notcontain any type of mechanism to control the accumulation of ice in thearea that is not effectively heated by the actuator.

U.S. Pat. No. 7,744,039 B2 [6] discloses a system and a method forcontrolling the flow from electrical pulses comprising multiple plasmaactuators and a controller which can be coupled to at least one of theelectrodes. High alternating voltage signals are used to controladjacent flow and short high voltage pulses are provided to protect fromaccumulation of ice. Although the above system makes use of DBD plasmaactuators for performing deicing, also in this case, the systempresented does not include an ice detector sensor, the area covered peractuator is limited and, since it only has one exposed electrode peractuator, it does not contain any type of mechanism to control theaccumulation of ice in the area that is not effectively heated by theactuator.

CN 102991666 A [7] discloses a laminated board for aircraft coatingwhich has lift-up features, resistance reduction, flow control andice-formation prevention functions. The aircraft laminate coatingcomprises an asymmetrically distributed DBD plasma actuator, which isconnected to a power supply capable of energizing the actuator with highalternating voltage or high voltage with nanosecond range pulses. Theice-formation prevention function is performed by means of air heatingdue to actuator operation and also by the wave pulse expansion function.Although the above system makes use of DBD plasma actuators forperforming deicing, this system does not include an ice detector sensor,the area covered per actuator is limited and, since it only has oneexposed electrode per actuator, it does not contain any type ofmechanism to control the accumulation of ice in the area that is noteffectively heated by the actuator.

CN 104890881 A [8] discloses a dielectric barrier discharge plasmadevice and an easy-to-use deicing method in aircraft coatings and whichenables rapid and efficient deicing of its coating. This devicecomprises a plasma actuator power supply and a plasma actuator, thelatter including an exposed electrode connected to the positive pole ofthe power supply, a covered electrode connected to the negative pole andan insulation layer. Although the above system makes use of DBD plasmaactuators for performing deicing, this system does not include an icedetector sensor, the area covered per actuator is limited and, since itonly has one exposed electrode per actuator, it does not contain anytype of mechanism to control the accumulation of ice in the area that isnot effectively heated by the actuator.

WO2014122568 A1 [9] relates to a system for preventing ice formation onaircraft surfaces, comprising a plasma actuator, which allows togenerate a plasma discharge for induction of the flow towards thesurface on which it is applied. Although this system uses DBD typeplasma actuators, its functions only provide for the formation of ice,unlike the present invention, which includes a deicing function.Furthermore, the invention disclosed in said document also does notcontain any kind of functionality, which allows the detection of iceformation and, as such, does not provide for continuous monitoring toverify the effectiveness of prevention, which functionality iscontemplated in the invention we propose wherein the actuator alsofunctions as a sensor. The area of plasma extension is limited becauseit does not provide for the use of a sliding electrode that allows toincrease the plasma extension and does not yet foresee the use of shockwaves that prevent the aggregation of ice in areas that are noteffectively heated by the operation of plasma actuators. This limitationis also overcome by the system we propose because we use a thirdelectrode that allows extending the area of plasma extension and alsoallows the production of shock waves that expel the ice from thesurface.

US 20080023589 A1 [10] describes systems and methods for flow controlfrom electrical pulses. The systems and methods described in saiddocument specifically use two electrodes and one dielectric layer,thereby providing a system dissimilar to the system described herein,which is based on the use of three electrodes, two exposed ones and onecovered, and which give the actuator extension capacity of the plasmadischarge zone, as well as the possibility of using shock waves, whichprevent a new accumulation of ice in the area that is not effectivelyheated by operation of the actuator. On the other hand, the presentedsystem does not provide any functionality for detecting ice formation.The invention referred to in the document is technically distinguishedfrom the invention proposed herein since it does not provide for the useof a sliding electrode, thus presenting limitations at the level of theplasma extension area.

US20110135467 A1 [11] describes a system for wind turbine blade deicingwhich includes a plasma actuator, applied to the desired surfaceportion, which increases the surface temperature so as to reduce oreliminate ice accumulation. The system presented uses conventionalplasma actuators, which does not provide for the use of athree-electrode plasma actuator, with a sliding electrode for increasingthe plasma extension, and shock-wave generation functionality to expelthe ice from the area that is not effectively heated by the actuator. Inaddition, the system disclosed in said document does not also have anice detection capacity.

The use of electric fields and capacitive sensors for detecting the icethickness has been reported in various documents which include patentsU.S. Pat. No. 4,766,369 A [12] and U.S. Pat. No. 5,398,547 A [13]. Inthese documents, systems and methods of measuring ice thickness on asurface are described by generating an electric field between twoelectrodes. These systems are limited only to detecting ice thickness.In the present invention, ice detection is performed not by atwo-electrode sensor, but rather by a three-electrode plasma actuator,which acts as a sensor and actuator simultaneously. Thus, the presentinvention enables ice detection through an actuator, which, in addition,can prevent the formation and/or promote the elimination thereof on themost critical aircraft surfaces.

The present invention makes use of sliding actuators with dielectricbarrier discharge, in which one of the electrodes can be energized bypulses of the nanosecond order, which allows the formation of a moreextensive plasma region, which in turn enables the coating of a largerarea per each set of actuators. In addition, using high voltage withnanosecond pulses, the actuator provides faster surface heating and theshock waves originated near the surface expel the ice and remove theportions of ice that accumulate after the effective heating area of theactuator. In addition, the present invention further acts as an iceformation sensor, which can be used to detect the onset of ice formationand indicate when a critical ice formation point is reached. On theother hand, by using circuit-printing technology, wide networks ofactuators including temperature sensors can be manufactured, which canbe easily printed together with the actuators.

GENERAL DESCRIPTION

Under favourable conditions, ice formation can occur from thecondensation of water droplets on the front edge of the aircraft wing.Ice accumulations are more frequent on the front edge of the wings, tailand engines, including propellers or turbine blades. Ice accumulationcan lead to weight gain, creating aerodynamic imbalances, local flowdisturbance, reduced performance, critical loss of control or lift,premature loss of aerodynamics, and increased resistance. Thus, in orderto prevent ice formation on the surface of aircrafts, it is necessary toemploy an adequate system of protection against ice accumulation. An iceprotection system acts as an anti-icing system, preventing itsformation, and/or acting as a deicing system, spilling the ice before itreaches a thickness deemed dangerous.

Deicing can be undertaken by different methods including mechanicalmethods, heat generation, use of chemicals (liquid or gaseous, designedto reduce the freezing temperature of water) or a combination of variousmethods. Each of these methods has advantages, but also drawbacks suchas high weight, energy consumption or the use of hazardous materials. Inaddition, some of these anti-icing and deicing methods are mechanicaland highly complex and, in some cases, undermine aerodynamicperformance. On the other hand, the function of most of these systems islimited to the control of ice and, when there are no conditionsfavourable to the formation of ice, they become useless and unnecessaryfor the improvement of flight performance.

The invention described herein consists of a novel ice control systemwhich includes a unique ice detection system and an anti-icing/deicingmechanism based on a three-electrode configuration, which makes it muchmore efficient. This system has low power consumption, increases theperformance and resistance of the fuselage or engine, and requireslittle maintenance. Furthermore, it has no drawbacks in terms ofaerodynamic performance, such as increased resistance, and can be usedas an actuator for flow control. This ice control system is anice-forming control system composed of anti-icing, deicing and directice detection technology, based on a dielectric barrier dischargesliding plasma actuator (FIG. 1). This invention integrates varioustechnologies along with its advantages including dielectric barrierdischarge plasma actuators for flow control and surface heating, slidingdischarge for obtaining a more extensive discharge area, nanosecondrange pulse discharges for a fast surface heating, detection of ice fromelectrical field disturbances caused by the presence of ice and waterdroplets, and manufacture of this electric circuit board from printingtechnology. This technology takes advantage of the fact that the DBDplasma actuator can be used for both flow control and surface heating.Therefore this system is able to control the flow and simultaneouslyperform the deicing on surfaces. DBD plasma actuators have been ofincreasing interest in recent years for their use in a variety ofapplications. The DBD plasma actuator releases energy during thedielectric discharge, which increases the temperature of the ice bymelting it and releasing it from the surface. These actuators canoperate in different modes depending on the type of voltage supplysignal. When the DBD operates with high AC voltage the surfacetemperature can reach temperatures above 80° C. for an applied voltageof 8 kVpp, wherein these temperature values can be exceeded depending onthe characteristics of the dielectric material. In this way, the ionicwind created by the plasma actuator improves the heating of the surfacefrom the convection of the heated air to the surface. On the other hand,when a DBD is energized by nanosecond pulsed voltage, the temperaturenear the surface is increased (400 K (126.85° C.) for pulses withduration of 50 ns) without directing the flow to the surface. It isassumed that vorticity is created by the shock wave, which is producedfrom the hot gas layer generated during the rapid heating process inwhich more than 60% of the discharge energy is converted into heatwithin a period of less than 1 μs. It is assumed that the heat output ofthe plasma actuator consists of the energy deposited by the neutral ioncollisions, elastic electron collisions, rotational excitation andvibrational excitation. The heating of the surface of plasma actuatorsis related to the power dissipated by the plasma discharge and to thethermal losses in the dielectric. The amplitude of the applied voltageand frequency influences the power dissipated by the plasma actuator.Therefore, in this invention a system for controlling the voltage andfrequency amplitudes is also considered.

Typical DBD plasma actuator devices comprise two electrodes separated bya dielectric barrier. The protected area of ice accumulation by thepresent invention depends on the length of the plasma discharge region.A group of plasma actuators consisting of a set of three electrodes,known as sliding discharge actuators, is considered in this invention toprovide a more extensive plasma region. These sliding DBD actuators arecomposed of two electrodes embedded on either side of the dielectriclayer, such as in a conventional DBD device, and also a second exposedelectrode fed by a direct voltage. This results in a sliding of thecharge space between the two electrodes exposed to air [14]. Thisdischarge is as stable as the discharge from a simple DBD plasmaactuator and has the advantage that it can be used in large scaleapplications because the extension of the discharge can be increasedover the entire distance present between the two exposed electrodes. Bysliding discharge the plasma region is greatly increased, the ionic windcreated near the surface is thicker and the maximum velocity of the jetproduced is slightly increased. Water droplets from melting ice in theregions protected by the DBD actuator may re-freeze again in the areawhere the DBD actuator is not as effective generating a secondary icelayer. This is because the temperature of the surface heated by theplasma decreases along the plasma region. Therefore, in order to extendthe deposition of energy on the surface by the DBD sliding plasmaactuator, the second exposed electrode of the actuator operates on apositive/negative continuous voltage with a tendency for nanosecondrange pulses. Thus, by means of rapid surface heating and also theformation of micro-shockwaves, this system also acts as a system thatprevents reforming of ice in the area behind the effective deicing area.Thus, the advantages of the sliding discharge and the advantages of aDBD actuator energized by nanosecond range pulses are combined.

Ice sensors can also be integrated into the protection system againstice accumulation allowing more information to be gained, which in turnhelps to increase the efficiency of the device. In most aircraft icedetection systems, sensors cannot be placed exactly on the wing surfacessince they must be free from possible ice formations. On the other hand,the addition of salient sensors seriously damages the aerodynamics ofthe aircrafts. Although several attempts have been made to produce icedetectors these are limited by their accuracy, their inability todistinguish ice and water [15] and their inability to measure icethickness. DBD plasma actuators can be considered as a capacitor systemand, consequently, the present invention employs the same principles ofoperation as an ice capacitor detector and uses the DBD plasma actuatoras an ice detector sensor. Several capacitive ice detectors aredescribed in the literature for detecting layers of ice on a surface.The physical value of a capacitor depends on the dielectric constant ofthe insulation material. The electrical properties of water are changedaccording to their physical state (solid, liquid or gaseous), so if forexample, we have water vapour between the electrodes of the capacitorand it solidifies to form ice, the capacity value of the capacitor willvary. When a voltage differential is applied between the electrodes, anelectric current is induced through the capacitor, which leads to anaccumulation of electrons. The difference between ice and water can bedetermined from the measurement of changes in the dielectric constant,and this measurement can be performed from the measurement of theelectrode load.

Printing technologies such as inkjet printing can be used to produce anetwork of DBD plasma actuators allowing the coating of large surfaces.Circuit printing technologies have received wide attention as a viablealternative to the production of actuators and sensors due to thesimplicity of processing steps, reduction of materials used, lowmanufacturing costs and simple standardization techniques. In addition,this technology allows the control of the thickness and amount of inkapplied, allows a good definition of the printed areas and thepossibility of developing systems on surfaces that are not planarallowing the systems to adapt according to the desired requirements. Thewide variety of materials available for printing (conductors,semiconductors and dielectrics) as well as the possibility of developingnew formulations allow the production of DBD plasma actuators fromprinting techniques [16, 17]. Coupling of sensors and actuators allowsthe reduction of the size of the DBD actuator allowing the same controleffect at lower voltages and thereby increasing efficiency.

DESCRIPTION OF THE DRAWINGS

FIG. 1: Block diagram of the protection system against ice accumulation,in which (1) represents the exposed AC electrode, (2) represents thedielectric layer, (3) represents the embedded electrode, (4) representsthe sliding/nanosecond electrode, (5) represents the ground plane, (6)represents the AC power supply, (7) represents the DC power supply, (8)represents the nanosecond range pulse generator, (9) represents themonitoring capacitor, (10) represents the high voltage probe, (12)represents the temperature sensor, (13) represents the control signalinput module and (14) represents the monitoring system.

FIG. 2: Variation of the electric field due to different contaminationsa) without contamination b) ice surface d) water

In which (1) represents the exposed AC electrode, (2) represents thedielectric layer, (3) represents the embedded electrode, (4) representsthe sliding/nanosecond electrode, (15) represents the ice layer, (16)represents the water layer, (17) represents the electric field.

FIG. 3: I) Images obtained by Infrared techniques II) Spatial variationof temperature along the x axis III) Spatial variation of temperaturealong the y axis. For a) 0.3 mm Kapton b) 0.6 mm Kapton c) 1.12 mmPolycarbonate+Kapton. In which (1) represents the exposed AC electrode.

FIG. 4: Dielectric barrier discharge for two different applied voltages.In which (3) represents the embedded electrode, (18) represents theplasma discharge region, (1) represents the exposed AC electrode and(19) represents the length of the plasma.

FIG. 5: Different components of the DBD sensor/actuator deicing system.In which (1) represents the exposed AC electrode, (2) represents thedielectric layer, (4) represents the sliding/nanosecond electrode, (3)represents the embedded electrode, (20) represents a wing profile, (21)represents the sensor/actuator applied to the front surface of the wing,(18) represents the plasma discharge region, (22) represents the waterdroplets, (23) represents the ice layer in the area behind the effectivearea of the plasma, (24) represents the flow lines, (25) represents theice layer in the front area of the wing.

FIG. 6: Multiple DBD plasma actuators for flow control on curvedsurfaces. In which (26) represents the curved surface, (1) representsthe exposed electrode AC, (3) represents the embedded electrode and (18)represents the plasma discharge region.

FIG. 7: Network of DBD sensor/actuator systems manufactured from circuitprinting technology. In which (27) schematically represents the wing ofan aircraft, (28) represents the network of sensors/DBD actuatorsmanufactured as a sheet, (1) represents the exposed AC electrode, (2)represents the dielectric layer, (3) represents the embedded electrode,(4) represents the sliding/nanosecond electrode.

MATCHING NUMBERS

-   (1): represents the exposed AC electrode.-   (2): represents the dielectric layer.-   (3): represents the embedded electrode.-   (4): represents the sliding/nanosecond electrode.-   (5): represents the ground plane.-   (6): represents the AC power supply.-   (7): represents the DC power supply.-   (8): represents the nanosecond range pulse generator.-   (9): represents the monitoring capacitor.-   (10): represents the high voltage probe.-   (11): represents the control module.-   (12): represents the temperature sensor.-   (13): represents the control signal input module.-   (14): represents the monitoring system.-   (15): represents the ice layer.-   (16): represents the water layer.-   (17): represents the electric field.-   (18): represents the plasma discharge region.-   (19): represents the length of the plasma.-   (20): represents a wing profile.-   (21): represents the sensor/actuator applied to the front surface of    the wing.-   (22): represents water droplets.-   (23): represents the ice layer in the area behind the effective area    of the plasma.-   (24): represents the flow lines.-   (25): represents the ice layer in the front area of the wing.-   (26): represents a curved surface.-   (27): represents the wing of an aircraft.-   (28): represents the network of sensors/DBD actuators manufactured    as a sheet.

DETAILED DESCRIPTION

This invention comprises a dielectric barrier discharge plasma actuatorcomposed of three electrodes. FIG. 1 shows the physical outline of thisnovel invention where the high voltage electrodes can be distinguishedfrom the dielectric barrier material (usually a high temperatureresistant polymer, glass, Kapton or Teflon). Referring particularly toFIG. 1, a simple sensor/actuator of this invention comprises: adielectric layer (2), two electrodes positioned on the surface of thedielectric layer, wherein the exposed AC electrode (1) is energized withAC voltage and the sliding/nanosecond electrode (4), which is alsoexposed, is energized by a continuous voltage with a tendency fornanosecond pulses and an embedded electrode (3) which is not exposed toair and is connected to the ground plane (5). In another embodiment, theexposed voltage-energized electrode is also energized with nanosecondvoltage pulses in the range of 10 ns to 100 ns.

One of the electrodes is covered by a dielectric material and theremaining electrodes are exposed to free flow. Also observed in FIG. 1is the use of a DC power supply (7), an AC power supply (6) and ananosecond range pulse generator (8). The electrodes are connected to ahigh voltage generator. Preferably, the distance between the exposedelectrode and the embedded electrode can be optimized in order toincrease the performance of the plasma actuator. The power supply isconfigured to generate alternating current with frequency magnitudes inthe order of kilohertz and voltage amplitudes in the order of kilovolt.Particularly the power supply can cause a modulated voltage. When thehigh voltage AC signal, which is applied to the exposed AC electrode(1), has sufficient voltage amplitudes (5-80 kVpp) and frequencies (1-60kHz) a dynamic electric field change is produced and the intenseelectric field ionizes partially the adjacent air producing non-thermalplasma on the dielectric surface. Ionized air propagates from the frontside of the exposed AC electrode (1) to the embedded electrode (3)creating a plasma track. The dielectric layer does not readily lead thecurrent, so it prevents the formation of electric arc between theelectrodes, which allows the electric field to suck the air down andform the plasma. The difference in potential applied leads to the changeof charged ions in the plasma and some of these ions collide with theadjacent air molecules, which bounce in the same direction creating theso-called ionic wind. In this way, the plasma actuator accelerates thesurrounding fluid. In this mode, the main flow control mechanism passesby movement induction to the adjacent flow. When the sliding/nanosecondelectrode 4 is energized at the same time with a DC voltage with atendency for nanosecond range pulses, a large plasma sheet is formed onthe upper surface of the dielectric layer which covers the entiresurface between the exposed AC electrode (1) and the sliding/nanosecondelectrode (4), which in turn is also exposed. Collisions between neutralparticles and accelerated ions give rise to a body force in thesurrounding fluid leading to the formation of the so-called ionic wind.Body force can be used to induce a desired flow control of a fluidsystem. For the DBDs the amount of plasma and fluid movement induces aninitial vortex propagating downstream from the exposed AC electrode (1)to the sliding/nanosecond electrode (4). The existence of the dielectricbarrier introduces a region of high electric field force breakdown andtherefore leads to high intensities in the plasma region. The dischargeof plasma generated by the DBD triggers the ionization of the particlescontained in the gas that is in the surrounding environment. Gas andsurface heating due to plasma formation is caused by the work done byelectric field ions, by the extinction of electronically energizedspecies and by the impact of the elastic electrons with the ambient gas.The heat generated by the ionization is transmitted directly to thesurface and is then positioned by the ionic wind thus preventing theformation of ice on that surface. In fact, a large part of the heat thatis transferred to the dielectric layer derives from the convexity of thehot air flowing on its surface. The plasma actuator used in thisinvention is a DBD type actuator, which generates the so-callednon-thermal plasma. The temperature of the ionized particles in thistype of plasma is typically within the range of 40° C. to 100° C., andas such the presence of plasma has no destructive effects on thematerials to which they are applied. The shape of the DBD electrodes mayoptionally be changed to circular or serpentine forms in order to obtaindifferent force fields and associated flows. This system also comprisesa control module (11) that can automatically control the power suppliesaccording to a predetermined criterion, allowing the automatic switchingbetween ice, anti-icing and deicing detection modes of operation, basedon the fact that the heating of the surface caused by the formation ofplasma will increase with the increase of the applied voltage and thevoltage applied in the ice detection mode is much lower than the voltageapplied in the anti-icing and deicing modes. The system also includes atleast one temperature sensor (12) whose output signal is used to analysethe formation of ice on the surface. The sensor allows determining thepresence of freezing conditions. If there is a possibility of freezingconditions, the system operates in ice detection mode in order toindicate the presence of ice. Other control signals, for examplerelative to weather conditions, may optionally be supplied to the systemfrom the control signal input module (13). The control module can easilyswitch between modes, and in the absence of favourable conditions forice formation, the system can then be used as a flow control device.However, in case of detection of ice formation on the surface, thecontrol module activates the power supply by appropriately adjusting theinput signals of the exposed electrodes and the system starts running indeicing mode. The operating voltage is measured from a high voltageprobe (10) and the current consumed by the DBD plasma actuator isobtained by measuring the voltage to the terminals of the monitoringcapacitor (9) which is connected to the ground plane (5). The voltageand current measured during operation of the system can be obtained bythe user from the monitoring system (14). The DBD is used as an icedetector sensor in a manner similar to a capacitive sensor. Since thepermissivities of air, water and ice are different, the accumulation ofcharge on the surface of the dielectric material will also be different.From the measurement of the effect of each material on the electricfield or the load on the surface the different materials can beidentified. FIG. 2 shows the electrical field disturbances near thesensor-actuator surface due to external contaminations such as water andice layer. The exposed AC electrode (1) in this mode operates with acertain voltage and the embedded electrode (3) and thesliding/nanosecond electrode (4) act as charge receptors. The electricfield (17), close to the surface, makes it possible to distinguish thepresence of an ice layer (15) or a water layer (16) partially coveringthe surface. Using this principle, the DBD functions as an ice detectorsensor. The energized voltage that is required for ice detectionpurposes is low and can be defined according to the capacity used formeasuring surface charges. The ice sensor accordingly notifies thesystem on the existence of ice so that it can melt precisely andcarefully the ice where it is needed and only when it is needed.

FIG. 3 shows thermal images obtained by Infrared techniques and thespatial variation of the temperatures along x and y of conventional DBDplasma actuators but with different layers of dielectric material. Inthis Figure, (1) represents the exposed AC electrode. As the appliedvoltage increases, the heating of the surface provided by the plasmaactuator is improved. This is used as the basis for the control system,which controls the supply voltage and from this control it can switchbetween the anti-icing and deicing modes. If a layer of thinnerdielectric material is used the heating effect is also improved.Therefore, thinner dielectric layers can also be used in the manufactureof the present invention in order to improve its efficiency in surfaceheating.

FIG. 4 shows the plasma surface extension for typical plasma actuatorswith two electrodes with applied voltages of different amplitudes, where(3) represents the embedded electrode, (18) represents the plasmadischarge region, (1) represents the exposed AC electrode and (19)represents the length of the plasma. When the applied voltage isincreased, the plasma surface extends over a larger area. This againconfirms that the control system can be used to change the appliedvoltage depending on the different purposes of deicing or anti-icingoperation.

FIG. 5 demonstrates an ice protection system on the surface of a wingusing multiple sensors and DBD actuators. The different layers of thesystem including the electrodes and the dielectric layer are shown, inwhich (1) represents the exposed AC electrode, (2) represents thedielectric layer, (3) represents the embedded electrode, (20) representsa wing profile and (21) represents the sensor/actuator applied to thefront surface of the wing representing one of the most critical areasfor ice formation. By using multiple sensors/actuators it is thenpossible to cover larger surfaces. When an ice layer is formed in thefront area of the wing (25), the actuator system will be activated indeicing mode by rapidly removing the ice from the surface. In this casethe exposed AC electrode (1) will be energized with high AC voltage andat the same time the sliding/nanosecond electrode will be fed withnanosecond pulse high voltage. In view of the formation of plasma on thesurface, the surface temperature of the wing increases to a temperaturehigher than the melting temperature of the water. The formation ofmicro-shockwaves together with a rapid heating of the sliding/nanosecondelectrode (4) will separate the ice layer from the surface. Thus, theice present on the front edge of the wing is melted and poured out bythe flow around the wing. A few drops of water (22) resulting from thedeicing performed on the front edge of the wing will be drawn by theflow to the surface of the wing. If the rear part of the wing is notprotected, then an ice layer forms in the area behind the effective areaof the plasma (23). A portion of this reforming ice layer will be meltedby the heat produced by the pulse electrode in the nanosecond range andthe remaining portion will be melted by the second sensor/actuator whichis installed on the surface.

FIG. 6 shows multiple DBD actuators for flow control on curved surfaces.In this FIG. 26) represents the curved surface, (1) represents theexposed AC electrode, (3) represents the embedded electrode and (18)represents the plasma discharge region. Since DBD sensors/actuators arecomposed of thin, flexible layers of electrodes and dielectric material,they can be used on a variety of surfaces including flat or curvedsurfaces. Therefore, they can be applied to practically all kinds ofsurfaces.

FIG. 7 schematises a top view of an aircraft wing equipped with anetwork of these DBD sensor/actuator systems, manufactured from circuitprinting technology as flexible surfaces embedded in the wing surfaceand exposed to air, wherein (27) represents the wing of an aircraft,(28) represents the network of DBD sensors/actuators manufactured as asheet, (1) represents the exposed AC electrode, (2) represents thedielectric layer, (3) represents the embedded electrode, and (4)represents the sliding/nanosecond electrode. The DBD sensor/actuatorsets are staggered between each other and are connected in parallelforming a sensor/actuator network capable of covering the entireaerodynamic surface. This network of actuators comprises a number offlexible sheets each containing multiple DBD sensors/actuators intendedto be applied to surfaces for control thereof and prepared to generatemultiple plasma discharges in order to induce a flow of ionized hotparticles in the direction of the surface. By using circuit printingtechnology, customizing the dimensions of the DBD sensors/actuators issomething that is done with extreme ease. The production of continuousand flexible bands of DBD sensor/actuator networks from printingtechnology also ensures the reduction of installation and maintenancecosts.

APPLICATION EXAMPLES

The present invention has various industrial applications such asdeicing and flow control in aircraft components including fixed wings,stabilizers, jet engine inlet, engine inlet, helicopter rotor blades,rotary blades, air turbine blades.

It can also be applied as a deicing system in critical tubular systems.

REFERENCES

-   [1] E. MERLO, A. Gurioli, E. MAGNOLI, G. MATTIUZZO, R. PERTILE,    System for preventing icing on an aircraft surface operationally    exposed to air, WO 2014122568 A1, 2014.-   [2] S. G. Saddoughi, B. J. Badding, P. Giguere, M. P.    Boespflug, J. G. A. Bennett, A. Gupta, System for deicing a wind    turbine blade, EP 2365219 A2, 2011.-   [3] S. G. Saddoughi, B. J. Badding, P. Giguere, M. P.    Boespflug, G. A. Bennett, A. Gupta, System and method of deicing and    prevention or delay of flow separation over wind turbine blades,    2011.-   [4] G. Herbaut, D. Bouillon, Splitter nose with plasma de-icing for    axial turbomachine compressor, CA 2908979 A1, 2016.-   [5] G. CORREALE, I. Popov, Boundary layer control via nanosecond    dielectric/resistive barrier discharge, WO 2015024601 A1, 2015.-   [6] R. B. Miles, S. O. Macheret, M. Shneider, A. Likhanskii, J. S.    Silkey, Systems and methods for controlling flows with electrical    pulses, 2010.-   [7] W. Guang-qiu, X. Bang-meng, Y. Guang-quan, Laminated plate    aircraft skin with flow control and deicing prevention functions, CN    102991666 A, 2013.-   [8] C. Jinsheng, T. Yongqiang, M. Xuan-shi, Z. Qi, Icing removing    device and method of dielectric barrier discharge plasma, CN    104890881 A, 2015.-   [9] E. Merlo, A. Gurioli, E. Magnoli, G. Mattiuzzo, R. Pertile,    System for preventing icing on na aircraft surfasse operationally    exposed to air, WO2014122568 A1, 2014.-   [10] R. Miles, S. Macheret, M. Shneider, A. Likhanskii, J. Silkey,    Systems and methods for controlling flows with electrical pulses, US    20080023589 A1, 2008.-   [11] S. G. Saddoughi, B. J. Badding, P. Giguere, M. P.    Boespflug, G. A. Bennett, JR, A. Gupta, System and method of deicing    and prevention or delay of flow separation over wind turbine blades,    US20110135467 A1, 2011.-   [12] L. M. Weinstein, Ice detector, U.S. Pat. No. 4,766,369 A, 1988.-   [13] J. J. Gerardi, G. A. Hickman, A. A. Khatkhate, D. A. Pruzan,    Apparatus for measuring ice distribution profiles, U.S. Pat. No.    5,398,547 A, 1995.-   [14] Surface Dielectric Barrier Discharge Plasma Actuators, (n.d.).-   [15] G. W. Codner, D. A. Pruzan, R. L. Rauckhorst, A. D.    Reich, D. B. Sweet, Impedance type ice detector, U.S. Pat. No.    5,955,887 A, 1999.-   [16] V. Correia, C. Caparros, C. Casellas, L. Francesch, J. G.    Rocha, S. Lanceros-Mendez, Development of inkjet printed strain    sensors, Smart Mater. Struct. 22 (2103) 105028.-   [17] S. Khan, L. Lorenzelli, R. S. Dahiya, Technologies for Printing    Sensors and Electronics Over Large Flexible Substrates: A Review,    IEEE Sens. J. 15 (2015) 3164-3185.

1. Ice detection/protection system with ice detection, anti-frost anddefrost operating modes and flow control comprising at least onedielectric barrier discharge plasma actuator, DC power supply, AC powersupply, a high voltage probe, a nanosecond range pulse generator, and acontrol module, applicable on any surface; wherein the dielectricbarrier discharge plasma actuator is connected in series with amonitoring capacitor, acts as an ice-forming sensor, and comprises adielectric layer and three electrodes.
 2. System according to claim 1,wherein the power supplies controlled by the control module switchesbetween the ice detection, anti-frost and defrost operating modes. 3.System according to claim 1, wherein the nanosecond range pulsegenerator generates a pulsed voltage with a duration between 10 ns to100 ns.
 4. System according to claim 1, wherein two electrodes areexposed and positioned on the surface of the dielectric layer.
 5. Systemaccording to claim 1, wherein one of the electrodes is covered by thedielectric layer.
 6. System according to claim 1, wherein the threeelectrodes are: an exposed AC electrode is energized by AC voltage; thean exposed sliding/nanosecond electrode energized by DC voltage with atendency for nanosecond pulses; an embedded electrode which is separatedfrom the electrodes exposed by the dielectric material, is not exposedto air and is connected to the monitoring capacitor which is connectedto a ground plane.
 7. (canceled)
 8. System according to claim 1, whereinin the anti-frost and defrost modes the AC voltage from the AC powersupply has an amplitude between 5 and 80 kVpp and frequencies between 1and 60 Hz.
 9. System according to claim 1, wherein the monitoringcapacitor is connected to the ground plane and monitors variations ofthe electric field of the plasma actuator.
 10. System according to claim1, further comprising at least one temperature sensor.
 11. Systemaccording to claim 1, further comprising a control signal input module.12. System according to claim 11, wherein in case of ice formation, thecontrol module activates the AC power supply and the DC power supply,which adjusts the input signals from the exposed electrodes.
 13. Systemaccording to claim 1, wherein an operating voltage is measured from thehigh voltage probe.
 14. System according to claim 1, further comprisinga monitoring system.
 15. System according to claim 1, wherein the plasmaactuator is manufactured by circuit printing technology with embeddedtemperature sensors.
 16. (canceled)